Pluto Flyby Begins: NASA Probe Enters Encounter Phase

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NASA's New Horizons probe has officially begun to execute its
sequence of Pluto flyby observations as it zooms toward its
closest approach to the dwarf planet on July 14.

Mission representatives say New Horizons is "back on track" after
it
experienced an anomaly on July 4 that caused it to go into a
temporary "safe mode." The anomaly was later shown to be the
result of too many commands being executed at once.

The spacecraft is already collecting data about the Pluto system,
and its nine-day flyby sequence will continue through July 16.
It's taken more than nine years for the $700 million New Horizons
mission to traverse the 3 billion miles (4.8 billion kilometers)
between Earth and Pluto, but the peak of the spacecraft's journey
will last a matter of hours. [ Photos
of Pluto and Its Moons ]

As the probe nears Pluto, NASA TV will air daily updates from
mission control at the Johns Hopkins University Applied Physics
Laboratory in Laurel, Maryland, at 11:30 a.m. ET (1530 GMT),
through July 14.

In an update Wednesday (July 8), Alice Bowman, mission operations
manager for
New Horizons, said the July 4 anomaly gave the mission team a
bit of a scare.

"We were all a little bit afraid of what might happen, but we put
on our engineering hats and we went down our checklist and we did
what needed to be done to recover that spacecraft to operational
mode," Bowman said.

New Horizons returned to nominal science operations on Tuesday
(July 7). Mission team members reported that about 30
observations were lost during those three days. Those data
represent "less than 1 percent of the total science that the New
Horizons team hoped to collect between July 4 and July 16," NASA
said in
a statement.

"We're delighted with the New Horizons response to the anomaly,"
Jim Green, NASA's director of planetary science, said in the
statement. "Now we're eager to get back to the science and
prepare for the payoff that's yet to come."

Bowman said the spacecraft is currently taking science
data as well as optical navigation data, which is "very
important because it is a measure of how well we are doing on
that trajectory to hit that specific point at the specific time
that the science team wants us to hit. So that's pretty much what
we're focused on now, is to get those science observations at the
right time and at the perfect lighting conditions.